Sure thing, let's get straight to it. We start with 873 and we're going to multiply it by 25, which means adding 873 to itself 25 times.
Step 1: 0 + 873 = 873
Step 2: 873 + 873 = 1746
Step 3: 1746 + 873 = 2619
Step 4: 2619 + 873 = 3492
Step 5: 3492 + 873 = 4365
Step 6: 4365 + 873 = 5238
Step 7: 5238 + 873 = 6111
Step 8: 6111 + 873 = 6984
Step 9: 6984 + 873 = 7857
Step 10: 7857 + 873 = 8730
Step 11: 8730 + 873 = 9603
Step 12: 9603 + 873 = 10476
Step 13: 10476 + 873 = 11349
Step 14: 11349 + 873 = 12222
Step 15: 12222 + 873 = 13095
Step 16: 13095 + 873 = 13968
Step 17: 13968 + 873 = 14841
Step 18: 14841 + 873 = 15714
Step 19: 15714 + 873 = 16587
Step 20: 16587 + 873 = 17460
Step 21: 17460 + 873 = 18333
Step 22: 18333 + 873 = 19206
Step 23: 19206 + 873 = 20079
Step 24: 20079 + 873 = 20952
Step 25: 20952 + 873 = 21825

So, 873*25 = 21825